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Calcium-Binding Protein Protocols Calcium-Binding Protein Protocols

Calcium-Binding Protein Protocols Calcium-Binding Protein Protocols

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Spatial Distribution of Ca 2+ -<strong>Binding</strong> <strong>Protein</strong>s 393<br />

Fig. 6. Reaction mechanism for the synthesis of the two major fluorescent peaks<br />

(7 and 9) in singly labeled FL-calmodulin. In the longer peptide (residues 75–86), the<br />

probe is intramolecularly cyclized between two amino groups by substitution of both<br />

chlorines and as reaction conditions favored Lys 75 labeling, it is expected that the probe<br />

is cyclized on this residue rather than Lys 77. In the case of the short peptide (residues<br />

75–77), 5-DTAF is bound only to Lys 75 by substitution of only one of the chlorines<br />

and so in this case is not cyclized.<br />

longer peptide (residues 75–86), the probe is intramolecularly cyclized between<br />

two amino groups by substitution of both chlorines and as reaction conditions<br />

favored Lys 75 labeling, it is expected that the probe is cyclized on this residue<br />

rather than Lys 77. In the case of the short peptide (residues 75–77), 5-DTAF is<br />

bound only to Lys 75 by substitution of only one of the chlorines and so in this<br />

case is not cyclized.<br />

9. The materials and methodology used for characterization of Lys 75 and Lys 148<br />

doubly labeled FL-calmodulin are identical as described for singly labeled<br />

FL-calmodulin. However, the tryptic digests of doubly labeled FL-calmodulin<br />

and singly labeled FL-calmodulin show two important differences. A new<br />

absorption and fluorescent peak appears at position 12, which corresponds to the<br />

second labeled site not seen in singly labeled FL-calmodulin. Also, a reduced<br />

absorption peak at position 10 is seen since this peptide fragment becomes<br />

labeled, reappears as fluorescent peptide peak 12 (see Fig. 3). Figures 9 and 10

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